Eyewear having a flexural member

ABSTRACT

An eyewear article having a flexing portion including first and second longitudinally disposed ribs is disclosed. In another exemplary embodiment, the flexing portion has a maximum height (H), in a direction parallel to a mid-sagittal plane bisecting the eyewear into imaginary left and right halves, that is greater than 10 mm. The eyewear article of the present invention provides a balance of fit and comfort suitable for a range of user head sizes.

TECHNICAL FIELD

This invention relates to eyewear for a person that exhibits an improvedfit, in particular eyewear offering an improved fit on a range of headsizes.

BACKGROUND

Eyewear articles, such as eyeglasses intended to correct a person'svision, and safety glasses, intended to protect a person's eyes or facefrom harm, are widely known. Both types of eyewear often rest on thenose, and above or on each ear of a user. A user's perception of howwell eyewear fits may be influenced by how well the eyewear fits on thenose and over the ears, perhaps together with whether the lenses of theglasses are too close to the person's eyes or face, or other factors.

Prior eyewear articles have attempted to provide comfortable eyewear byspecifying an eyewear article for use on individuals having a particularhead size. In addition, many designs incorporate features such as springhinges, or mechanisms that allow the eyewear to be adjusted for aparticular wearer. Such approaches result in increased costs due tocomplicated design and manufacturing requirements, or a need to stockmultiple sizes of each eyewear design.

Ultimately, there is a continued need for better fitting eyewear,suitable for use by large groups of users.

SUMMARY

Glossary

In reference to the invention, the following terms are defined as setforth below:

“and/or” means “and”, “or”, and a combination of “and” and “or.”

“angularly disposed” when referring to ribs of a flexing portion meansthe ribs are not parallel such that one or more major surfaces of theribs form an angle that is not within 5° of 180°.

“attachment portion” means a feature of the lens, frame, or othersuitable feature that a temple piece may be secured to.

“contact portion” when referring to the contact portion of a templepiece means the portion that contacts the head of a user just aboveand/or behind the normal position of the ear.

“flexing portion” refers to a portion of a temple piece that flexes whensubjected to an appropriate force, as when an eyewear article ispositioned for use on the head of a user, for example.

“flexural modulus” means the ratio of stress to strain in flexuraldeformation, and may be measured according to ASTM D790 or ISO 178, forexample.

“force exerted at a contact portion” means the force exerted in adirection generally normal to the surface of the contact portion uponthe head of a user, for example, and/or the corresponding force exertedby the head of the user on the contact portion, and may be measured at alocation approximately 110 mm from the frontal plane of an eyeweararticle when the eyewear article is positioned for use.

“lens” means a structure through which a user can see the surroundingenvironment and may include any suitable material.

“portion” means part of a larger thing.

“positioned for use” when referring to an eyewear article means theeyewear article is positioned generally in front of the eye or eyes of auser to provide the intended functionality of the eyewear article.

“unflexed state” when referring to the temple piece or flexing portionof an eyewear article means a neutral state in which little or no forcesare exerted at a contact portion of the temple piece.

“radius of curvature” means the radius of an osculating circle at apoint of a curve, consistent with the traditional mathematical meaningof the term.

“width” when used to describe the width of a human head refers to thedistance between a point just above the normal position of each ear.

The present invention provides for an eyewear article having a templepiece extending rearwardly from a front of an eyewear article thatincludes a flexing portion having a maximum height (H) in a directionparallel to a mid-sagittal plane, the mid-sagittal plane bisecting theeyewear article into imaginary left and right halves. The flexingportion includes first and second longitudinally disposed ribs eachhaving first inner surfaces that form an angle θ1 when the temple pieceis in an unflexed state and that form an angle θ2 when in a flexedstate, such that θ1<θ2. In some embodiments, the first and second ribsare connected along the lengths of the ribs. The eyewear article furtherincludes a contact portion, and the contact portion may be orientedsubstantially vertically when the eyewear article is positioned for useon a human head. In some embodiments, the eyewear article includes morethan two longitudinally disposed ribs, and each rib comprises first andsecond major surfaces separated by a thickness (t), and the first majorsurfaces of each rib is not perpendicular with respect to a transverseplane bisecting the eyewear article into imaginary upper and lowerhalves. In some embodiments, H is greater than 24 mm, or the flexingportion further includes third and fourth longitudinally disposed ribs,and when the temple piece is in an unflexed state the third rib isangularly disposed with respect to the fourth rib. In variousembodiments, the flexing portion has a torsional stiffness about itslongitudinal axis that is greater than 32 N-mm/rad, or greater than 56N-mm/rad. In various embodiments, the flexing portion is made of amaterial having a flexural modulus between 800 MPa and 1700 MPa, orbetween 1000 MPa and 1200 MPa. In some embodiments, the flexing portionhas a radius of curvature (ρ), and ρ<80 mm when the temple piece is inan unflexed state.

In some embodiments, each rib has first and second major surfacesseparated by a thickness (t), and comprises a length (l) in thelongitudinal direction of the rib and a height (h) in a directionperpendicular to each of the thickness (t) and the length (l), andwherein the first and second major surfaces of each rib aresubstantially planar. In various embodiments, h is between 2.5 mm and 8mm, t is between 0.5 mm and 2.5 mm, and/or l is between 15 mm and 45 mm.In some embodiments, the height (h) of each rib varies along the lengthof each rib.

An eyewear article according to the present invention may include atemple piece that is an injection molded plastic, and may be made of amaterial selected from the group consisting of polycarbonates,polyesters, polyamides, and acetals.

In some exemplary embodiments, the temple piece includes a contactportion, and a force (F) exerted normal to the contact portion isbetween 50 g and 110 g when the eyewear article is positioned for use ona human head having a width (W) between 130 mm and 170 mm. In someexemplary embodiments, F may be between 70 g and 110 g when the eyeweararticle is positioned for use on a human head having a width (W) between150 mm and 180 mm.

In some exemplary embodiments, the temple piece further includes acontact portion, and a first force (F1) is exerted normal to the contactportion when the eyewear article is positioned for use on a human headhaving a width of 130 mm, and a second force (F2) is exerted normal tothe contact portion when the eyewear article is positioned for use on ahuman head having a width of 180 mm, and (F2−F1)<50 grams.

The eyewear of the present invention may be safety glasses, goggles,sunglasses, cosmetic glasses, vision correction glasses, and/or othereyewear articles as known in the art. The above summary of the presentinvention is not intended to describe each disclosed embodiment or everyimplementation of the present invention. The Figures and the DetailedDescription, which follow, more particularly exemplify illustrativeembodiments. U.S. Patent Publ. No. 2013/0229615, titled “Eyewear Havingan Arcuate Flexural Member,” and U.S. Patent Publ. No. 2013/0229614 andfiled on Mar. 2, 2012, address the structure and configuration of anexemplary eyewear article having a flexing portion, and are incorporatedherein by reference.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will be further explained with reference to theappended Figures, wherein like structure is referred to by like numeralsthroughout the several views, and wherein:

FIG. 1 is a perspective view of an eyewear article according to thepresent invention.

FIG. 2 is a perspective view of an eyewear article according to thepresent invention defining several reference planes by which the eyeweararticle may be better understood.

FIG. 3 is a perspective view of a temple piece extending rearwardly froma front of an eyewear article having an exemplary flexing portionaccording to the present invention.

FIGS. 4 a through 4 c are side views of ribs of exemplary temple piecesaccording to the present invention.

FIGS. 5 a and 5 b are sectional views of exemplary temple pieces havinga flexing portion according to the present invention including ribs withfirst and second planar surfaces.

FIG. 6 is a sectional view of an exemplary temple piece having a flexingportion according to the present invention including ribs with first andsecond curved surfaces.

FIG. 7 is a top perspective view of an eyewear article according to thepresent invention having a temple piece and flexing portion withcurvature in an unflexed state.

FIG. 8 is a perspective view of an eyewear article according to thepresent invention having a flexing portion that includes fourlongitudinally disposed ribs.

FIG. 9 is a perspective view of a flexing portion according to thepresent invention that includes four longitudinally disposed ribs.

FIG. 10 is a side view of an exemplary embodiment of a flexing portionaccording to the present invention.

FIG. 11 is sectional view of an exemplary embodiment of a flexingportion according to the present invention.

DETAILED DESCRIPTION

The present invention provides an eyewear article having features thatprovide a balance of fit and comfort suitable for a range of head sizes.The eyewear article provides sufficient force at contact portions of atemple piece to maintain the eyewear article on a user having arelatively small head width, while providing a force within a desiredcomfort range when positioned on a user having a relatively large headwidth. In an exemplary embodiment, the eyewear article provides adesired level of force at contact portions of a temple piece that isless dependent on a user's head width than prior eyewear articles.

FIG. 1 shows a first exemplary embodiment of an eyewear article 100.Eyewear article 100 may include traditional eyewear components includingone or more lenses 130 or a frame. Eyewear article 100 includes twotemple pieces 110 each having a first end portion 111, a contact portion112, and a flexing portion 120. Temple pieces 110 extend rearwardly froma front of eyewear article 100. Flexing portion 120 has a radius ofcurvature when in an unflexed state. Flexing portion 120 flexesoutwardly to accommodate the head of a user, and is configured toprovide desired characteristics over a range of suitable head widths. Inan exemplary embodiment, contact portion 112 remains in a substantiallyconstant orientation independent of the flexure that the flexing portion120 is subjected to in accommodating a particular head width. Whenpositioned for use, eyewear article 100 is positioned generally in frontof the eye or eyes of a user to provide the intended functionality ofeyewear article 100. The one or more lenses 130 interact with a user'sfield of vision, or substantially block the user's eyes and portions ofa user's face from external elements.

In an exemplary embodiment, first end portion 111 of temple piece 110may be secured to an attachment portion 150 of the one or more lenses130, frame, or other suitable feature of eyewear article 100. Templepiece 110 may be secured to attachment portion 150 by any suitable meansknown in the art. For example, temple piece 110 may be rotatably securedwith a hinge that permits pivotal motion of temple piece 110 about anaxis at various positions between an open and closed position. This maybe achieved by first end portion 111 of temple piece 110 includingfeatures that mate with corresponding features of the one or more lenses130, a frame, or other suitable features of eyewear article 100, and aresecured in a rotatable engagement with a screw, pin, or other fasteneras known in the art. Temple piece 110 may be also attached using a snapfit attachment, for example. In another exemplary embodiment, eyeweararticle 100 may or may not include a frame, and temple pieces 110 may beattached to attachment points of the one or more lenses.

The components of eyewear article 100 described above may be formedseparately and subsequently joined together to form the eyewear article.In an exemplary embodiment, one or more lenses 130 and a frame areformed integrally as a single piece, such as by injection molding,transfer molding, compression molding, or other techniques as known inthe art. In another exemplary embodiment, temple pieces 110 may beformed by injection molding, transfer molding, compression molding, orother techniques known in the art, and subsequently joined to a lens orframe. Alternatively, various parts, or the entire eyewear article 100,may be formed integrally.

Flexing portion 120 may be formed from a material having suitableproperties to allow for elastic deformation over a range of normalbending that the temple piece and flexing portion may be subjected to.In an exemplary embodiment, temple piece 110 and/or flexing portion 120are made from an ultraviolet stabilized blend of polycarbonate andpolyester, such as a material having the trade name XYLEX X8300available from Sabic Innovative Plastics of Pittsfield, Mass., or ablend of polycarbonate and polybutelene, such as a material having thetrade name XENOY 5720 available from Sabic Innovative Plastics. In otherexemplary embodiments, temple piece 110 and/or flexing portion 120 aremade from a polycarbonate such as PC124R available from Sabic InnovativePlastics, or an acetal such as D100 ST available from E.I. Du Pont DeNemours and Co. Other suitable materials include other polycarbonates,polyesters, polyamides, acetals, thermoplastics, other suitablematerials as known in the art, and suitable combinations of suchmaterials.

In an exemplary embodiment, temple piece 110 and flexing portion 120 aremade of a material having a flexural modulus between 800 MPa and 2500MPa. In various exemplary embodiments, the flexural modulus may bebetween about 800 MPa and 1700 MPa, or between about 1000 MPa and about1200 MPa.

Certain features of an eyewear article according to the presentinvention may be understood in view of three reference planes definedrelative to eyewear article 100 and shown in FIG. 2. With eyeweararticle 100 positioned horizontal as when positioned for use, andviewing eyewear article 100 from the outer side of the lens, which maybe referred to as the front of the eyewear, mid-sagittal plane 161bisects eyewear article 100 into imaginary left and right halves.Transverse plane 162 divides eyewear article 100 horizontally intoimaginary upper and lower portions. Transverse plane 162 is generallyparallel to a plane of rotation formed by temple piece 110 as it movesbetween open and closed positions, and as it moves from an unflexedstate to a deflected state for accommodating the head of a user. Templepiece 110 is said to be in an open position when a hinge joining templepiece 110 to a frame or lens is fully opened, and temple piece 110remains in an unflexed state such that no load is exerted on or bycontact portion 112 of temple piece 110. Temple piece 110 is said to bein a closed position when a hinge is fully closed, such that templepiece 110 is folded inward, for example. Frontal plane 163 is orthogonalto both the mid-sagittal and transverse planes and substantiallytangential to the front-most portion of one or more lenses 130.

As shown in FIG. 2, the position of contact portion 112, and thecorresponding deflection of temple piece 110, may be characterized by adistance d, substantially parallel to transverse plane 162 of eyeweararticle 100 and perpendicular to mid-sagittal plane 161, that separatesthe contact portion from the mid-sagittal plane of eyewear article 100.For example, a first distance separates contact portion 112 frommid-sagittal plane 161 when temple piece 110 is in an open position andan unflexed state. When temple piece 110 is flexed to accommodate thehead of a user, as shown in phantom for example, a second distance dseparates contact portion 112 from mid-sagittal plane 161. The seconddistance d may be approximately one half the magnitude of the width ofthe head that eyewear article 100 is positioned on. When temple piece110 is flexed, a restoring force acts to return temple piece 110 to aposition in which it is not subject to flexure. The magnitude of theforce exerted at contact portion 112 of temple piece 110 for a givendeflection can be determined, and is related to the geometry andmaterials of the temple piece and of the eyewear article, as discussedfurther herein.

FIG. 3 shows a temple piece 110 extending rearwardly from a front of aneyewear article 100 having an exemplary embodiment of a flexing portion120 according to the present invention. Flexing portion 120 has a firstend 121 and a second end 122, and first and second longitudinallydisposed ribs 125 and 126 between first and second ends 121 and 122.Each rib has first and second major surfaces S1 and S2 separated by athickness t, and includes a length l in the longitudinal direction ofthe rib, and a height h in a direction perpendicular to each ofthickness t and length l. In various embodiments, l may be betweenapproximately 10 mm and 75 mm, or between 15 mm and 45 mm, or may beapproximately 30 mm.

In the exemplary embodiment shown in FIG. 3, inner peripheral edges ofeach of first and second ribs 125 and 126 define a slot 129 extendingbetween portions of first and second ribs 125 and 126. In alternativeexemplary embodiments, the inner peripheral edges may define a pluralityof slots, grooves, or other openings, or the first and second ribs maybe joined completely or partially along the lengths of the ribs byhaving connected inner peripheral edges, for example.

The thickness and height of ribs 125 and 126 may affect how flexingportion 120 bends and otherwise reacts when a force is applied to templepiece 110. Specifically, the thickness and height of ribs 125 and 126may affect the location where flexing portion 120 initially bends when aforce is applied to temple piece 110, and how the force is distributedthroughout flexing portion 120. In various exemplary embodiments, ribs125 and 126 may have a height h that is between 2 mm and 10 mm, orbetween 2.5 mm and 8 mm. In an exemplary embodiment, one or both of ribs125 and 126 may have a height h that varies between a minimum height anda maximum height. In such an embodiment, flexing portion 120 may beginto bend at or near the location of the minimum height of the rib when aninitial force is applied to the temple piece.

In an exemplary embodiment, the minimum height hmin of one or both ofribs 125 and 126 occurs at a position spaced from first and second ends121 and 122 of the flexing portion 120, as shown in FIG. 4 a forexample. In other exemplary embodiments, the height of each rib may beuniform as shown in FIG. 4 b, or may vary over the length of each ribfrom a maximum height hmax near first end 121 to a minimum height hminnear second end 122, as shown in FIG. 4 c, for example.

In an exemplary embodiment, first rib 125 is angularly disposed withrespect to second rib 126 when the flexing portion is in an unflexedstate, such that first major surfaces S1, major surfaces on the innerside of ribs 125 and 126, form an angle θ less than 180°. When templepiece 110 is flexed such that eyewear article 100 may be positioned foruse on the head of a user, for example, ribs 125 and 126 rotate relativeto one another such that angle θ becomes larger, as discussed in furtherdetail below. As shown in FIG. 5 a, for example, angle θ1 defined by thefirst planar surfaces S1 on the inner surface of each rib 125 and 126when temple piece 110 is in an unflexed state, is less than the angle θ2defined by the first planar surfaces S1 of each rib 125 and 126 whentemple piece 110 is flexed. In the deflected state, angle θ2 has a valuecloser to 180° than θ1 does, such that the surfaces S1 of each rib 125and 126 are closer to parallel. Because of the relative rotation of eachrib, the area moment of inertia of the cross-section about the bendingaxis is decreased. Accordingly, less force is required for a marginalchange in deflection of temple piece 110, and the force exerted atcontact portion 112 increases more slowly or remains constant withfurther increases in deflection, as described in greater detail below.

In another exemplary embodiment, first and second ribs 125 and 126 maybe angularly disposed such that second major surfaces S2, major surfaceson the outer side of each rib, form an angle θ less than 180° whenflexing portion 120 is in an unflexed state, as shown in FIG. 5 b. Whentemple piece 110 is flexed such that eyewear article 100 may bepositioned for use on the head of a user, first and second ribs 125 and126 rotate such that the angle θ decreases towards 180° or an angle lessthan 180°. As shown in FIG. 5 b, for example, the second planar surfacesS2 on the outer surface of each rib 125 and 126 define an angle θ3 whentemple piece 110 is unflexed that is less than an angle θ4 defined bythe second planar surfaces S2 of each rib 125 and 126 when temple piece110 is flexed. In the deflected state, angle θ4 has a value closer to180° than θ3 does, such that the surfaces S2 of each rib 125 and 126 arecloser to parallel.

In another exemplary embodiment, first rib 125 and/or second rib 126 areangularly disposed such that one or both of the first and second majorsurfaces S1 and S2 is not perpendicular to transverse plane 162 ofeyewear article 100, as shown in FIGS. 5 a and 5 b, for example. Thatis, one or both of first and second major surfaces S1 and S2 is notwithin 5° of forming a 90° angle with transverse plane 162 of eyeweararticle 100. When temple piece 110 is flexed such that eyewear article100 may be positioned for use on the head of a user, first and secondribs 125 and 126 rotate such that one or both of first and second majorsurfaces S1 and S2 are closer to being in perpendicular to a transverseplane 162 of eyewear article 100.

In an exemplary embodiment, as shown in FIGS. 5 a and 5 b, first andsecond ribs 125 and 126 each have a thickness t between the first andsecond planar surfaces S1 and S2 that decreases from an inner peripheraledge 123 to an outer peripheral edge 124. In some exemplary embodiments,first and second ribs may have a thickness t at any particular pointthat is between 0.5 mm and 5 mm. In other embodiments, thickness t maybe between 0.5 and 4 mm, or 0.5 mm and 2.5 mm. The flexing portionbecomes stiffer as the thickness of the ribs is increased, and mayresult in a greater force at a contact portion of the temple piece for aparticular temple separation as compared to a flexing portion havingribs with a smaller thickness.

In some exemplary embodiments, the thickness t may vary along the heightof a rib between a thickness t of about 0.5 mm at outer peripheral edge124 and a thickness t at inner peripheral edge 123 of about 2.5 mm, forexample. In other exemplary embodiments, first and second ribs 125 and126 have a thickness t that is constant across the height h of each rib,or a thickness t that increases from an inner peripheral edge 123 to anouter peripheral edge 124.

In some exemplary embodiments, the thickness tmax at inner peripheraledge 123 may remain constant along length 1 of each rib 125 and 126,while thickness tmin at outer peripheral edge 124 varies along length 1.In an exemplary embodiment, thickness tmax at inner peripheral edge 123is approximately 1.5 mm along length l, and tmin at outer peripheraledge 124 varies along length 1 from approximately 1.0 mm at each end toapproximately 0.5 mm at a location along length 1 of approximately 10 mmfrom the end of each rib nearest first end 321 of flexing portion 320.

In another exemplary embodiment, shown in FIG. 6, first and second ribs125 and 126 may exhibit first and second curved surfaces S1 and S2.Similar to the embodiments in which the ribs have first and secondplanar surfaces, the thickness of the ribs may be constant or may varyover the height of the rib. First and second ribs 125 and 126 each havea thickness t between first and second curved surfaces S1 and S2 thatdecreases from each inner peripheral edge 123 to each outer peripheraledge 124.

In other exemplary embodiments, first and second ribs 125 and 126 have athickness t that is constant, or a thickness t that increases from innerperipheral edge 123 to outer peripheral edge 124. Alternatively, theinner peripheral edges of first and second ribs 125 and 126 may beconnected, and the thickness t may vary across the height of each ribbetween each outer peripheral edge 124 and the point of connection ofthe inner peripheral edges 123 of the first and second ribs.

The curved surfaces of each rib 125 and 126 define a radius of curvatureof the ribs. The ribs are angularly disposed to one another when in anunflexed state, such that the ribs define a particular radius ofcurvature R1. When a force is applied to the temple piece 110, as whenthe eyewear article is positioned for use on the head of a user, firstand second ribs 125 and 126 may flex and/or rotate relative to oneanother such that the radius of curvature R2 becomes larger, asindicated by ribs 125 and 126 shown in phantom.

FIG. 7 shows an exemplary embodiment of an eyewear article 100 having atemple piece 110 according to the present invention. Temple piece 110has a flexing portion 120 that exhibits a curvature when in an unflexedstate. The curvature of flexing portion 120 can be defined by a radiusof curvature. A radius of curvature is the radius of an osculatingcircle at a point on a curve, and can vary from point to point on acurve. A tight curve is generally said to have greater curvature and alower radius of curvature, while a gentle curve is generally said tohave less curvature and a greater radius of curvature. When temple piece110 is deflected, to accommodate the head of a user for example, theradius of curvature of flexing portion 120 is increased. Accordingly,the curvature of an exemplary embodiment of a flexing portion 120 isgreater in an unflexed state than when the eyewear is positioned for useon the head of a user.

Flexing portion 120 of temple piece 110 is characterized by a radius ofcurvature ρ when the flexing portion 120 is in an unflexed state. In anexemplary embodiment, radius of curvature ρ of flexing portion 120 whenin an unflexed state is less than 80 mm. In other embodiments, theradius of curvature ρ of flexing portion 120 is between 20 mm and 60 mm,or between 45 mm and 55 mm, when flexing portion 120 is in an unflexedstate. In an exemplary embodiment, the radius of curvature ρ is constantor nearly constant along the length of flexing portion 120. For example,flexing portion 120 may have a maximum radius of curvature ρM and aminimum radius of curvature ρm, and the magnitude of the maximum radiusof curvature may be within 5 mm of the magnitude of the minimum radiusof curvature. In an exemplary embodiment, the radius of curvature oftemple piece 110 may be characterized as a radius of curvature at aparticular point that is a certain distance along a length of the templepiece. For example, in an exemplary embodiment, the radius of curvatureρ of flexing portion 120 at a distance of 30 mm from attachment portion150, or first end portion 111, along the length of temple piece 110, isbetween 20 mm and 80 mm.

A flexing portion having a radius of curvature as described aboveprovides several advantages to an eyewear article according to thepresent invention. A flexing portion exhibiting a low radius ofcurvature must undergo additional deflection to accommodate the head ofa wearer as compared to the deflection that a traditional temple piecelacking curvature would be subjected to when positioned on the samehead. That is, while a substantially straight temple piece undergoeslittle or no bending before the contact portions of each temple pieceare sufficiently separated to be positioned on the head of a user,temple pieces 110, and specifically flexing portions 120, of eyeweararticle 100 shown in FIG. 7 must undergo substantial deflection toaccommodate the head of a user. Accordingly, temple piece 110 havingsuch a flexing portion enters a stressed state with less separationbetween temple pieces 110 as compared to traditional eyewear. Sufficientforce to secure eyewear article 100 on the head of a user may beobtained even with a more flexible temple piece. Furthermore, the radiusof curvature present when flexing portion 120 is in an unflexed stateallows the flexing portion to function as desired within an appropriaterange of deflections corresponding to the majority of user head widths.That is, the specified curvatures of flexing portion 120 allow contactportion 112 of temple piece 110 to exert a desired level of force at aparticular temple separation. These and other advantages will be morefully understood with reference to the force displacementcharacteristics of a temple piece having a flexing portion according tothe present invention described below.

Eyewear articles including a flexing portion according to the presentinvention may provide a desired force at contact portions of the templepiece over a wider range of head sizes than previous eyewear articles. Asignificant portion of adult human heads have widths between 130 mm and170 mm, measured just above the normal position of each ear. Further,the present inventors have determined that a force between approximately40 grams and 140 grams, or between approximately 50 grams and 110 grams,or of approximately 80 grams, provides the optimal perceived balance ofsecurity and limited pressure such that an eyewear article will notinadvertently fall out of position and will not exert too much force soas to cause discomfort. Accordingly, exemplary eyewear article 100exhibits a force at a contact portion within the above desired rangewhen positioned for use on a human head having a width between 130 mm to170 mm. That is, the force at contact portion 112 of temple piece 110 iswithin a desired range when a distance d separating contact portion 112of each temple piece 110 from mid-sagittal plane 161 of eyewear article100, as described above with reference to FIG. 2, is between 65 mm and85 mm. In an exemplary embodiment, the force exerted normal to contactportion 112 is between 50 grams and 140 grams when eyewear article 100is positioned for use on a human head heaving a width between 130 mm and170 mm. In other exemplary embodiments, the force is between 50 gramsand 110 grams, and may be between 70 grams and 110 grams when eyeweararticle 100 is positioned for use on a human head having a width ofbetween 150 mm and 180 mm, or when d is between 75 mm and 90 mm.

A curve indicating force exerted at a contact portion versusdisplacement of a temple piece may be obtained for an eyewear article bymeasuring the force at various temple separations, for example byfollowing Procedure 1 described below. Without being bound by theory,the slope of such a curve is related to the flexibility of the measuredtemple piece. Accordingly, a more flexible temple piece will generallyresult in a force at a contact portion that varies less over a range ofdeflections as compared to a stiff temple piece in which a smallincrease in deflection results in a relatively large increase in forceexerted at a contact portion. In an exemplary embodiment, the forceexerted at contact portion 112 of temple piece 110 varies by 50 grams orless over a range of temple separations between 130 mm and 180 mm. Thatis, a first force F1 is exerted at contact portion 112 when eyeweararticle 100 is positioned for use on a human head having a width of 130mm, and a second force F2 is exerted at contact portion 112 when eyeweararticle 100 is positioned for use on a human head having a width of 180mm, and the difference between F2 and F1 is less than or equal to 50grams. In various other embodiments, the difference between F2 and F1may be less than 30 grams, or less than 20 grams. In contrast, manyprior designs exhibit forces that vary by significantly more than 50grams over a range of temple separations between 130 mm and 180 mm.

The minimum desired force level at contact portion 112 of temple piece110 can be obtained despite being constructed of a material havinggreater flexibility as compared to that of many traditional templepieces. Such a result is due in part to a combination of inherentcurvature exhibited by temple piece 110 and flexing portion 120 when inan unflexed state, and the presence of longitudinally disposed ribs asdescribed herein. In an exemplary embodiment, temple piece 110 undergoesdeflection even before the temple separation surpasses 80 mm. As aresult, a force at contact portion 112 reaches a value above 50 gramswhen the temple separation is greater than 130 mm despite temple piece110 having a greater flexibility than that of many prior eyeweararticles. Further, because of the relatively flexible temple piece 110facilitated by the inherent curvature of flexing portion 120, the forcelevel remains closer to a desired level through a greater range oftemple separations.

The force levels exerted at contact portion 112 exhibited by anexemplary embodiment of temple piece 110 is also attributable to thestructure and configuration of flexing portion 120. Without being boundby theory, force exerted at contact portion 112 of temple piece 110 ofthe present invention can be characterized as proportional to theproduct of the temple separation and the relevant area moment ofinertia. The area moment of inertia is calculated about an axisperpendicular to the longitudinal axis of temple piece 110, and in theplane of bending as is known in the art. As deflection increases, theforce at contact portion 112 increases, and as deflection decreases, theforce at contact portion 112 decreases. Similarly, as the area moment ofinertia of a cross-section of temple piece 110 increases, the force atcontact portion 112 increases, and as the area moment of inertiadecreases, the force at contract portion 112 decreases.

The area moment of inertia of prior temple pieces is believed to remainsubstantially constant when deflected such that a force exerted at acontact portion is generally proportional to deflection. In an exemplaryembodiment of flexing portion 120, however, the area moment of inertiaof a particular cross-sectional location changes as the temple piece isflexed to accommodate the head of a user. As described above, first andsecond ribs 125 and 126 rotate relative to one another as temple piece110 is deflected. As a result, the area moment of inertia at aparticular cross-section of flexing portion 120 changes as temple piece110 is deflected. For example, when the eyewear article is positionedfor use on a head having a first width, the area moment of inertia of across-section is greater than when the eyewear article is positioned foruse on a head having a second width that is greater than the firstwidth. Accordingly, the area moment of inertia of a cross-section of thetemple piece decreases as the flexing portion undergoes additionalflexure. In this way, rather than exhibiting an increase in the forceexerted at contact portions 112 of temple pieces 110 as temple pieces110 are deflected or flexed to accommodate increasing head widths, thearea moment of inertia is reduced. The force exerted at contact portion112 of temple piece 110 remains substantially constant, or exhibits lessvariation, over a range of deflection of temple piece 110, andaccordingly over a range of user head sizes.

In addition to the above described features and characteristics, the fitof an eyewear article may depend in part on the positioning of thetemple pieces about a user's head, and particularly the location andorientation with which a contact portion of the temple piece contacts auser's head. In an exemplary embodiment of a temple piece according tothe present invention, the contact portion may have a substantiallyplanar surface to maximize the area that contacts the head of the usersuch that the pressure exerted on the user is minimized Comfort may bereduced if, for example, only an edge of the contact portion contactsthe head of a user. Accordingly, a contact portion of an exemplarytemple piece according to the present invention remains in asubstantially vertical orientation at any position within a range oftemple separations corresponding to a desired range of head sizes, andremains in a plane substantially parallel to the transverse planedefined above. That is, an exemplary temple piece according to thepresent invention resists rotation about the longitudinal axis of thetemple piece, or rotation out of the plane defined by the temple piecein an unflexed state.

An exemplary embodiment of eyewear article 200 according to the presentinvention is shown in FIGS. 8 and 9. Eyewear article 200 may includetraditional eyewear components including one or more lenses 230 or aframe. Eyewear article 200 includes two temple pieces 210 each having aflexing portion 220 and a contact portion 212. Flexing portion 220 has afirst end 221 and a second end 222, and includes first and secondlongitudinally disposed ribs 225 and 226, and third and fourthlongitudinally disposed ribs 227 and 228. Each rib has first and secondmajor surfaces S1 and S2, on the inner and outer surfaces of each rib,respectively, and a height h in a direction perpendicular to a length inthe longitudinal direction of each rib. Further, flexing portion 220exhibits a maximum height H in a direction parallel to a mid-sagittalplane of the eyewear article. In an exemplary embodiment, the maximumheight H occurs at a position along temple piece 210 near end 221 offlexing portion 220. Various features and characteristics of eyeweararticle 200 may be defined relative to three reference plans describedabove with reference to eyewear article 100, and oriented as shown inFIG. 2.

In an exemplary embodiment, rib 225 is angularly disposed with respectto rib 226, and rib 227 is angularly disposed with respect to rib 228,such that first major surfaces S1 on the inner side of ribs 225 and 226,and ribs 227 and 228, respectively, form an angle less than 180°. Whentemple piece 210 is flexed such that eyewear article 200 may bepositioned for use on the head of a user, ribs 225, 226, 227 and 228rotate such that first major surfaces S1 of ribs 225 and 226, and ribs227 and 228, respectively, form an angle closer to 180° than in anunflexed state. In another exemplary embodiment, rib 225 is angularlydisposed with respect to rib 226, and rib 227 is angularly disposed withrespect to rib 228, such that the second major surfaces S2, on the outerside of ribs 225 and 226 and ribs 227 and 228, respectively, form anangle less than 180°. When temple piece 210 is flexed such that eyeweararticle 200 may be positioned for use on the head of a user, ribs 225,226, 227 and 228 rotate such that second major surfaces S2 of ribs 225and 226, and ribs 227 and 228, respectively, form an angle closer to180° than in an unflexed state. In another exemplary embodiment, one ormore of ribs 225, 226, 227, and 228 are disposed such that one or bothof first and second major surfaces S1 and S2 are not perpendicular tothe transverse plane of eyewear article 200. That is, one or both offirst and second major surfaces S1 and S2 are not within 5° of forming a90° angle with a transverse plane of eyewear article 200. When templepiece 210 is flexed such that eyewear article 200 may be positioned foruse on the head of a user, ribs 225, 226, 227 and 228 rotate such thatone or both of the first and second major surfaces S1 or S2 of ribs 225and 226, and ribs 227 and 228, respectively, are closer to being inperpendicular relation to the transverse plane of eyewear article 200.

In the exemplary embodiment shown in FIG. 9, slots 229 are definedbetween each rib. In alternative exemplary embodiments, the innerperipheral edges may define a plurality of slots, grooves, or otheropenings, and the first and second ribs may be joined completely orpartially along the lengths of the ribs, by having connected innerperipheral edges for example.

In an exemplary embodiment, longitudinally disposed ribs 225, 226, 227,and 228 are substantially identical to the ribs described above withreference to eyewear article 100, and function in a similar manner toproduce a desired force at contact portion 212 over a range of templeseparations. A flexing portion having four longitudinally disposed ribshas the functionality and advantages of a single pair of ribs, asdescribed herein, while providing further torsional stability such thatcontact portions 212 are more likely to remain in a desired orientation,for example a substantially vertical orientation, as temple piece 210 isdeflected to accommodate the head of a user. In an exemplary embodiment,flexing portion 220 has a torsional stiffness K about its longitudinalaxis that is greater than 32 N-mm/radian, or greater than 56N-mm/radian. Torsional stiffness can be defined as the ratio of anapplied torsion moment to an angle of twist, and can be used tocharacterize resistance to torsional rotation. A flexing portion havinga greater torsional stiffness requires a greater force to undergorotation about a longitudinal axis, and thus a temple piece having aflexing portion with a greater torsional stiffness is more likely toremain in a desired orientation as the temple piece is deflected toaccommodate the head of a user.

In various embodiments of the invention, the flexing portion has amaximum height H that is greater than 15 mm, or greater than 20 mm, orgreater than 24 mm. A flexing portion having a maximum height H asspecified above may include four longitudinally ribs, or may include twolongitudinally disposed ribs of relatively greater height. As themaximum height H increases, the torsional stiffness increases.Accordingly, a flexing portion having a maximum height H as specifiedabove is more likely to remain in a desired orientation as a templepiece is deflected to accommodate the head of a user.

In various embodiments, an eyewear article according to the presentinvention may include two, three, four, or more longitudinally disposedribs while obtaining the advantages and characteristics describedherein. In an exemplary embodiment, eyewear article 200 includes morethan two longitudinally disposed ribs, and each rib comprises first andsecond major surfaces separated by a thickness (t), and the first majorsurface of each rib is not perpendicular with respect to a transverseplane bisecting the eyewear article into imaginary upper and lowerhalves.

Exemplary temple piece 210 having the above describe features providessufficient torsional stability such that contact portion 212 remains ina substantially vertical orientation at any position within a particularrange of temple separations, and resists rotation about the longitudinalaxis of the temple piece.

An eyewear article having various features and combinations of featuresdescribed herein provides several benefits. Many prior art designsappear to exhibit a linear force-displacement response such that theforce exerted by a temple piece increases linearly with a relativelyhigh slope as the temple piece is deflected, and significantly differentlevels of force are exerted by a temple piece when the eyewear articleis positioned on heads having different widths. Accordingly, a singleeyewear article may provide different levels of comfort when used byindividuals having different head widths. In contrast to many priordesigns, an eyewear article according to the present invention providesa balance of fit and comfort over a range of head widths by providing aneyewear article that exhibits a non-linear force-displacement responseover a portion of a range of expected temple separations, or a linearforce-displacement response with a relatively low slope. Due to thecombination of a flexing portion that exhibits an area moment of inertiathat changes as the flexing portion is flexed, and a flexing portionhaving an inherent curvature, a single eyewear article may provide adesired force level on users having relatively small head widths as wellas on users having relatively large head widths. Further, the costsassociated with providing eyewear articles of different sizes to usershaving different head widths are reduced, and manufacturing costsassociated with designs incorporating complex or moving parts isminimized.

EXAMPLES

The characteristics, operation, and advantages of the present inventionwill be further described with regard to the following detailednon-limiting examples. These examples are offered to further illustratethe various specific and preferred embodiments and techniques. It shouldbe understood, however that many variations and modifications may bemade while remaining within the scope of the present invention.

Procedure 1: Force-Deflection Measurement

A measurement of the force exerted at a contact portion versusdeflection of a temple piece provides an indication of comfort that aneyewear article may exhibit over a range of head sizes. Values indicatedas temple separations are analogous to head widths, and areapproximately twice the distance d, described above, that separatescontact portion 112 of temple piece 110 from mid-sagittal plane 161 ofeyewear article 100. The force obtained for each temple separation iscomparable to the force that will be exerted at a contact portion whenthe eyewear article is positioned for use on a human head.

Force versus deflection data was obtained using a custom fixtureincluding a lens support and two Mark-10 MG05 force gauges, availablefrom Mark-10 Corp. of Long Island, N.Y. Each force gauge was mounted ontranslation stages and positionable with a drive screw such that a loadpost of each force gauge moved an equal distance from a center point ofthe fixture as the drive screw was turned. That is, each load post wasapproximately equidistant from a mid-sagittal plan dividing the eyeweararticle into imaginary left and right halves. A linear scale wasprovided to indicate the distance between the load posts of each forcegauge. The sample was placed on the fixture with the lens clamped to thelens support and each temple piece positioned to the outside of therespective load post. The initial distance between the load posts was 80mm, and the load posts contacted the temple piece at a distanceapproximately 110 mm from the front of the lens of the sample. Theseparation distance between each load post, and accordingly a contactportion of each temple piece, can be said to correspond to a head widthof equal magnitude. Force measurements were recorded from each load cellat 10 mm increments between 130 mm and 180 mm of load post spacing. Thetemple pieces were not clamped or fixed to the load posts, and were freeto move relative to the load posts as the separation distance betweenthe load posts was increased.

Examples 1 through 5

Examples 1 through 5 were measured according to Procedure 1. The sampleof Example 1 was VIRTUA® #70-0715-3942-6 safety glasses available from3M Company. The sample of Example 2 was GRAVITY ZERO #9191.265 safetyglasses available from Uvex Safety Group. The sample of Example 3 wasMONTEGO #SB5310S safety glasses available from Pyramex. The sample ofExample 4 was an eyewear article according to the present invention, andconstructed of a material referred to as XYLEX 8300, available fromSabic Innovative Plastics. The sample of Example 5 was an eyeweararticle according to the present invention, and constructed of amaterial referred to as D100 ST, available from DuPont.

The samples of Examples 4 and 5 were dimensioned consistent with theexemplary embodiments shown in FIGS. 7, 10, and 11. FIG. 7 provides ascale drawing of a top view of exemplary temple piece 110 according tothe present invention. The flexing portion has a radius of curvature ofapproximately 50 mm. FIG. 10 provides a side view of an eyewear articleaccording to the present invention. Each of ribs 325, 326, 327, and 328has a maximum height hmax of approximately 5 mm and a minimum heighthmin of approximately 2.5 mm. The length 1 of each rib is approximately30 mm. Slots 329 have a maximum width Wmax of approximately 1.5 mm, anda minimum width Wmin of approximately 0.8 mm.

FIG. 11 provides a sectional view at lines 11-11 of FIG. 10. Each ribhas a thickness that decreases from a maximum thickness tmax at innerperipheral edge 323, to a minimum thickness tmin at outer peripheraledge 124. Thickness tmax at inner peripheral edge 323 is approximately1.5 mm along the length l of each rib. Thickness tmin at outerperipheral edge 324 of each rib varies along the length of the rib froma thickness of approximately 1.0 mm at each end to a thickness ofapproximately 0.5 mm at a distance along length l of approximately 10 mmfrom the end of each rib nearest first end 321 of flexing portion 320.An angle θ formed by the inner surfaces S1 of each of ribs 125 and 126at a midpoint of the length of ribs 125 and 126 is approximately 155°.

TABLE 1 Temple Separation Force (g) (mm) Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5Sample/Material VIRTUA GRAVITY ZERO MONTEGO XYLEX 8300 D100 ST 130 16.863.5 105.5 53 43.5 140 50 86 113.2 69.5 55 150 69.5 108.5 120.7 83.566.5 160 90.9 130 125.7 95 73 170 125.8 154.5 129.2 102 75 180 153.7 175129.5 108 74.5

Table 1 indicates the force in grams measured at a contact portionaccording to Procedure 1 for Examples 1 through 5. The samples ofExamples 1 through 3 lacked flexing portions having longitudinallydisposed ribs according to the present invention, and did not providedesired force levels, for example levels between 50 and 140 grams, overa range of temple separations.

Example 1 failed to provide desired force levels over an entire range ofnormal head sizes between 130 mm and 180 mm. When the temple separationof the sample of Example 1 was 130 mm, the force exerted at a contactportion was less than 20 grams. Such a value is below a desired range,and a user having a head width of approximately 130 mm may perceive theeyewear to be insecure. Similarly, when the temple separation of thesample of Example 1 approached 180 mm, the force exerted at a contactportion exceeded 150 grams. As a result, the eyewear article is likelyto cause excessive pressure on the head of a user, resulting indiscomfort. Ultimately, the force exerted at a contact portion of thesample of Example 1 falls within a desired level only for a narrow rangeof head sizes as compared to the samples of Example 4 or 5, for example.

The sample of Example 2 similarly failed to provide desired force levelsover an entire range of normal head sizes between 130 mm and 180 mm. Ata temple separation of 150 mm, the force exerted at a contact portionexceeded 100 grams. At a temple separation of 180 mm, the force exertedat a contact portion was 175 grams. Accordingly, discomfort is likely toresult when such eyewear is worn by a user having a head width of 180mm.

The force exerted at a contact portion of the sample of Example 3 variesonly between 105.5 grams and 129.5 grams, but is consistently above adesired level of force within a range of temple separations between 130mm and 180 mm. Accordingly, the force at a contact portion is likelygreater than necessary to provide the optimum level of security, and maycause discomfort to a user.

The samples of Examples 4 and 5 provided desirable force levels over arange of temple separations. The sample of Example 4, having featuresaccording to the present invention, exhibited a force level ofapproximately 50 grams at a temple separation of 130 mm. Such a force iswithin a desired range, and will provide a perceived balance of securityof fit and comfort. As the temple separation increased through values upto 180 mm, the force remained below 110 grams. In the sample of Example5, force exerted at a contact portion was approximately 73 grams at atemple separation of 130 mm, and remained nearly constant through templeseparations of 180 mm. In contrast to the traditional eyewear ofExamples 1 and 2, the sample of Example 5 did not exert a level of forceat a contact portion likely to be uncomfortable, even when the templeseparation approached 180 mm.

Ultimately, the samples of Examples 4 and 5 provided desirable forcelevels over a range of temple separations such that sufficient force wasgenerated to provide a secure fit for relatively small head widths,while the maximum force was limited to a comfortable range whenpositioned on a head having a relatively large width.

Procedure 2: Torsional Stiffness Measurement

A temple piece having greater torsional stiffness may resist rotationabout the longitudinal axis of the temple piece, or rotation out of theplane defined by the temple piece in an unflexed state, such that thecontact portion remains in a substantially vertical orientation at anyposition within a range of temple separations corresponding to a desiredrange of head sizes. Comfort of an eyewear article may be reduced if,for example, only an edge of a contact portion of an eyewear articlecontacts the head of a user, resulting in areas of focused pressureimpinging upon a user's head. Accordingly, a temple piece having agreater torsional stiffness may be less likely to rotate such that onlyan edge of a contact portion contacts the head of a user.

Torsional characteristics of flexing portions of exemplary temple pieceswere obtained according to the following procedure. Samples were putinto rotation from a rest position over angles in which torque versusrotation was substantially linear. The material response was elastic inthis region such that torsional stiffness K was approximately equal tothe measured reactive torque T divided by the angle of rotation φ inwhich the flexing portion was forced to twist due to coupled action ofrotation of the motor with each sample. The resultant K was the computedtorsional stiffness in ounce-inch/degree, and was converted inN-mm/radian.

A torsion test fixture was built to measure torque response of theflexing portion of eyewear temple pieces. The fixture consisted of aModel TFF325 torque cell having a 20 inch-ounce (˜141.23 N-mm) fullscale capacity, available from Futek Advanced Sensor Technology, Inc. ofIrvine, Calif., a TMO-1 signal conditioner available from TransducerTechniques of Temecula, Calif., and TracerDaq software for dataacquisition available from Measurement Computing of Norton, Mass. Thefixture further included an Omega HT23-597 rotational stepper motorusing SI programmer V2.7.19 for motor control, and associated mechanicalfixtures for coupling a sample to the rotation stage and torque cell.

The portion of the temple piece extending beyond the flexing portion,including the contact portion, was trimmed from each sample in order tominimize the effects of inherent curvature of the sample or level armeffects on the resultant torque during testing. The resultant samplelength was 50 mm.

Samples were fixtured such that the cut end was attached to the steppermotor and the opposite end was attached to the reaction torquetransducer, and the angle between the axis of the rotational motor'sshaft and torque cell was adjusted so that the temple section to betested was substantially free of preloads, shear, compression, tensionor bending. The motor shaft was actuated via software at a rate of0.00139 revolutions per second in a clockwise direction such that thesample experienced clockwise twisting when viewing the temple from thefront as when attached to an eyewear article. A command set-point of 10°maximum rotation was used to maintain the sample in an elastic region.

After data acquisition, torque T was plotted versus angle of rotation φand torsional stiffness was obtained as the linear curve fit of thedata.

Examples 6 through 11

Examples 6 through 11 were obtained using procedure 2 described above.The samples of Examples 6 through 11 were flexing portions according tothe present invention and were dimensioned consistent with FIGS. 7, 10,and 11, as described above. The samples of Examples 7, 9, and 11 wereclipped to remove each of ribs 327 and 328, such that only ribs 325 and326 remained. The samples of Examples 6 and 7 were flexing portionsconstructed of D100 ST acetal resin, available from DuPont. The samplesof Examples 8 and 9 were flexing portions constructed of PC124Rpolycarbonate resin, available from Sabic Innovative Plastics. Thesample of Examples 10 and 11 were constructed of XYLEX 7300polycarbonate resin, available from Sabic Innovative Plastics.

TABLE 2 Torsional Stiffness Torsional % (K) (oz-in/ Stiffness (K)increase in # of degree) (N-mm/rad) stiffness of 4 Example # MaterialRibs (Computed) (Equivalent) rib sample 6 D100 ST 4 0.124 50.2 ~258 7D100 ST 2 0.048 19.4 8 PC124R 4 0.266 108 ~350 9 PC124R 2 0.076 30.7 10XYLEX 4 0.146 59.1 ~298 7300 11 XYLEX 2 0.049 19.8 7300

Table 2 indicates the torsional stiffness of Examples 6 through 11 asmeasured according to Procedure 2 described above. Samples 6, 8, and 10having four ribs exhibited a substantially greater torsional stiffnessthan samples 7, 9, and 11 having two ribs. The flexing portions ofExamples 6, 8, and 10 having a torsional stiffness of 50.2, 108, and59.1 N-mm/rad, respectively, provided a desirable level of torsionalstiffness of greater than 32 N-mm/rad. The flexing portions of Examples8 and 10 provided a desirable level of torsional stiffness of greaterthan 56 N-mm/rad.

Ultimately, examples having four ribs, and a greater height H, exhibitedgreater torsional stiffness. Contact portions of a temple piece havingsimilar flexing portions would be less likely to rotate out of the planeof bending, and less likely to cause discomfort due to only an edge ofthe contact portion contacting the head of a user. Samples 7, 9, and 11exhibited a relatively low torsional stiffness, and were more likely torotate out of the normal plane of bending of the temple piece.

The present invention has now been described with reference to severalembodiments thereof. The foregoing detailed description and exampleshave been given for clarity of understanding only. No unnecessarylimitations are to be understood therefrom. It will be apparent to thoseskilled in the art that many changes can be made in the embodimentsdescribed without departing from the scope of the invention. Thus, thescope of the present invention should not be limited to the exactdetails and structures described herein, but rather by the structuresdescribed by the language of the claims, and the equivalents of thosestructures. Any feature or characteristic described with respect to anyof the above embodiments can be incorporated individually or incombination with any other feature or characteristic, and are presentedin the above order and combinations for clarity only.

What is claimed is:
 1. An eyewear article, comprising: a temple pieceextending rearwardly from a front of an eyewear article having a flexingportion having a maximum height (H) in a direction parallel to amid-sagittal plane, the mid-sagittal plane bisecting the eyewear articleinto imaginary left and right halves; wherein the flexing portioncomprises first and second longitudinally disposed ribs and the flexingportion exhibits an area moment of inertia at a particularcross-sectional location, and wherein the area moment of inertia of theflexing portion at the particular cross-sectional location changes asthe temple piece is deflected, and wherein the flexing portion furthercomprises third and fourth longitudinally disposed ribs, and when thetemple piece is in an unflexed state the third rib is angularly disposedwith respect to the fourth rib.
 2. The eyewear article of claim 1,wherein the area moment of inertia at the particular cross-sectionallocation is greater when the eyewear is positioned on a head having afirst width than when the eyewear is positioned for use on a head havinga second width that is greater than the first width.
 3. The eyeweararticle of claim 1, wherein the area moment of inertia at the particularcross-sectional location decreases as the flexing portion is flexed. 4.The eyewear article of claim 1, wherein H>20 mm.
 5. The eyewear articleof claim 1, wherein the eyewear article further comprises a contactportion, and the contact portion is oriented substantially verticallywhen the eyewear article is positioned for use on a human head.
 6. Theeyewear article of claim 1, wherein each rib comprises first and secondmajor surfaces separated by a thickness (t), and the first major surfaceof each rib is not perpendicular with respect to a transverse planebisecting the eyewear article into imaginary upper and lower halves. 7.The eyewear article of claim 1, wherein the flexing portion has atorsional stiffness about its longitudinal axis that is greater than 32N-mm/rad.
 8. The eyewear article of claim 1, wherein the flexing portionis made of a material having a flexural modulus between 1000 MPa and1200 MPa.
 9. The eyewear article of claim 1, wherein each rib comprisesfirst and second major surfaces separated by a thickness (t), andcomprises a length (1) in the longitudinal direction of the rib and aheight (h) in a direction perpendicular to each of the thickness (t) andthe length (1), and wherein the first and second major surfaces of eachrib are substantially planar.
 10. The eyewear article of claim 9,wherein 2.5 mm<h<8 mm.
 11. The eyewear article of claim 9, wherein 0.5mm<t<2.5 mm.
 12. The eyewear article of claim 9, wherein 15 mm<1<45 mm.13. The eyewear article of claim 9, wherein the height (h) of each ribvaries along the length of each rib.
 14. The eyewear article of claim 1,wherein the temple piece comprises a material selected from the groupconsisting of polycarbonates, polyesters, polyamides, and acetals.